Electronic devices, such as integrated circuit chips, must be tested following manufacture so as to assure that they have acceptable performance, within their prescribed specifications. Operating speeds of electronic devices are becoming so fast that the devices frequently outperform available test equipment. Additionally, many electronic devices operate on mixed analog signals and digital signals, and so require tests of an analog nature and tests of a digital nature. Although mixed signal testers, capable of testing both analog characteristics and digital characteristics of a device, are known, they generally are unable to provide accurate test results on both analog signals and digital signal. Therefore, in the past separate analog and digital test set ups have generally been utilized to perform acceptance testing of such electronic devices. Not only are multiple pieces of test equipment required, but also an analog test procedure and a separate digital test procedure must be conducted. Consequently, the testing of mixed signal electronic devices is complex, time consuming, and expensive.
FIGS. 1 and 2, for example, illustrate a known testing arrangement and procedure for testing a mixed signal electronic device. The arrangement includes analog test set up 101 and digital test set up 103. The analog procedure starts in step T1, and in step T2 tester driver 102 of analog test set up 101 provides an input test signal through a tester interface unit 104 to mixed signal electronic device under test 106. In step T3, the resulting output test signal from device 106 is applied through tester interface unit 108 to tester receiver 110. Tester 112 receives inputs from tester driver 102 and from tester receiver 110 and in step T4 processes analog data from the device output signal. Tester 112 might be an analog tester or a mixed signal tester. In step T5 tester 112 determines whether the analog data are acceptable. If not, then in step T6 tester 112 adjusts the test signal, and the process returns to step T2. If the analog data are acceptable, then in step T7, tester 112 determines whether device 106 is acceptable. If so the device is accepted in step T8, and the process ends in step T9. If step T7 determines that device 106 is not acceptable, the device is rejected in step T10, and the process ends in step T9.
Once the analog testing is completed, device 106 is moved to digital test set up 103 and the digital test procedure starts in step T11. In step 112 tester driver 114 provides an input test signal through a tester interface unit 116 to mixed signal device 106. In step T13, the resulting output test signal from device 106 is applied through tester interface unit 118 to tester receiver 120. Processor 122 receives inputs from tester driver 114 and from tester receiver 120 and in step T14 processes digital data from the device output signal. In step T15 processor 122 determines whether the processed digital data are acceptable. If not, then in step T16 processor 122 adjusts the test signal, and the process returns to step T12. If the digital data are acceptable, then in step T17, tester 122 determines whether device 106 is acceptable. If so, the device is accepted in step T18, and the process ends in step T19. If step T17 determines that the device is not acceptable, the device is rejected in step T20, and the process ends in step T19. This testing requires two test set ups 101 and 103 and two test procedures. Alternatively, if tester 112 is a mixed signal tester, the device is left there, and the digital test procedure is performed on it. In either case, it is expensive and time consuming to test a mixed signal device.
In addition, the accuracy of the test equipment itself must be assured. The electronic device under test is to be utilized as a part of an overall system. In such use, the electronic device is generally mounted on a circuit board, such as a motherboard, and is electrically connected to other components on the circuit board. During testing, however, the electronic device is connected to test equipment which may not accurately emulate the performance of the components on the circuit board. During such testing, the electronic device is provided with an input signal from the test equipment and applies an output signal to the test equipment; whereas, in use the input signal is received from another component on the circuit board, and the output signal is provided to a further component on the circuit board. The test equipment which provides the input test signal and receives the output test signal generally includes a general purpose tester that is utilized during testing of numerous types of electronic devices, and a tester interface unit that is specially designed for use with the specific electronic device under test. Even though the test equipment is designed to emulate the other circuit components on the motherboard, that emulation is not total. By way of example, signal propagation times may be different. Output impedances, particularly capacitances, may differ. In general, the integrity of the input and output signals is different during testing as compared with during actual use. As a result, performance on the test equipment does not accurately emulate the performance on the circuit board. This problem is exacerbated when there are multiple types of electronic devices, and so multiple types of inputs and outputs, on the circuit board.
Further, in designing a new electronic device, a proposed design often is simulated on a processing system and evaluated at various points in the design process so that any need for design changes can be made and tested, The processing system emulates not only the electronic device, but also test arrangements and procedures for the device. Again, both analog and digital characteristics of the design of a mixed signal electronic device must be tested.